In recent years, an organic EL device has been intensively studied and put to practical use. The organic EL device is basically built up of a tin-doped indium oxide (ITO) or other transparent electrode, a triphenyldiamine (TPD) or other hole transporting layer laminated on the transparent electrode, an organic light emitting layer formed of a fluorescent material such as an aluminum quinolinol complex (Alq.sup.3) and laminated thereon, and a metal electrode (electron injecting electrode) provided on the organic light emitting layer and formed of a material having a low work function, for instance, Mg. Such a device now attracts attention as displays for use on household electrical appliances, car and bicycle electric equipment, etc., because a luminance of as high as several hundred to tens of thousands of cd/m.sup.2 is obtained at a voltage of about 10V.
Such an organic EL device has a structure wherein an organic layer such as a light emitting layer is sandwiched between a scanning (common line) electrode that usually provides an electron injecting electrode and a data (segment line) electrode that usually provides a hole injecting electrode (transparent electrode), and formed on a transparent (glass) substrate. Electroluminescent displays are generally broken down into a matrix display wherein scanning electrodes and data electrodes are arranged in a matrix form to display information such as images and characters in the form of an assembly of dots (pixels), and a segment display comprising independently provided display units each having predetermined shape and size.
The segment type display may be driven in a static driving mode where the display units are independently driven. For the matrix display, on the other hand, a dynamic driving mode is used, wherein scanning lines and data lines are usually driven in a time division fashion. The dynamic driving mode is classified into two driving modes, one wherein the electron and hole injecting electrodes are driven as scanning and data lines, respectively, and the other wherein the electron and hole injecting electrodes are driven as data and scanning lines, respectively.
The organic EL device may be expressed in terms of an equivalent electrical circuit, as shown in FIG. 8. In FIG. 8, the organic EL device is represented in the form of a parallel circuit comprising a diode element D and a parasitic capacity Cp, and so has a parasitic capacity. Therefore, when organic EL devices are arranged and connected together as shown in FIG. 9 for instance, the respective parasitic capacities of the organic EL devices (pixels) connected to scanning lines are added up. Thus, a time constant is provided by the sum of the parasitic capacities (e.g., EL1+EL4+EL7+ . . . ) and pull-up resistance components connected to those electrodes or resistance components such as on-resistance components of push-pull switching elements when a push-pull circuit is used.
Here, the matrix circuit constructed as shown in FIG. 8 is built up of switching elements SW11 to SW13 for driving scanning lines COM1 to COM3 (connecting them to the ground side or opening them), resistance components R1 to R3 (e.g., push-up resistance components or push-pull resistance components when a push-pull circuit is used) for stabilizing the scanning lines COM1 to COM3 at a given potential (power source potential) when these switching elements SW11 to SW13 are in non-operation (off), organic EL devices (pixels) EL1 to EL9, capacity components of these pixels EL1 to EL9, data lines SEG1 to SEG3 connected to the other ends of the pixels EL1 to EL9, and switching elements SW21 to SW23 for connecting these data lines to the driving power source or ground side.
When matrix circuit is driven in a time division fashion, the scanning electrode COM1 which reaches an L level upon turned on at a time t11 is turned off at a time t12, as shown in FIG. 10 for instance, so that when the scanning line goes back to an H level, there is a delay time Td due to the time constant defined by the parasitic capacities and the resistance components such as pull-up resistance components. This delay time Td overlaps the on-time Ton of the next scanning line COM2 at the time t12 to tn (t13, t14 . . . ) with the result that although depending on the data line condition, some pixels at the scanning line emits light for this delay time irrespective of being a non-selected pixel.
As shown in FIG. 11 as an example, when eyeing a certain group of pixels on the matrix, a pixel G appears, which gives rise to false light emission halfway between a lighting (driving) pixel L and a non-lighting (non-driving) pixel D or is brighter than in non-light emission state. Such false light emission makes contrast worse or is perceived as anomalous light emission, resulting in considerable drops of the quality of the display or a disturbance factor in images.
The case where electron and hole injecting electrodes are driven as scanning and data lines, respectively, has been explained. However, it is understood that when electron and hole injecting electrodes are driven as data and scanning lines, too, similar phenomena arise.